Alleviating the Hubble-constant tension and the growth tension via a transition of absolute magnitude favored by the Pantheon+ sample

TL;DR

This paper proposes a model-independent method to analyze supernova data, revealing a low-redshift transition in absolute magnitude that alleviates the Hubble constant and growth tensions in cosmology.

Contribution

It introduces a novel, model-independent approach to detect absolute magnitude variation, providing evidence for a transition that reduces key cosmological tensions.

Findings

Deviation from $ m extLambda$CDM at low redshift in supernova data

Transition in absolute magnitude $M$ improves Hubble constant estimates

Variation in $M$ linked to modifications in Newton's constant resolves growth tension

Abstract

We establish a cosmological-model-independent method to extract the apparent magnitude and its derivative at different redshifts from the Pantheon+ type Ia supernova sample, and find that the obtained values deviate clearly from the prediction of the $\Lambda$CDM model at the lowest redshift. This deviation can be explained as a result of a transition of the absolute magnitude $M$ in the low redshift region. The observations seem to favor this transition since the minimum values of $\chi^2$ for two ansatzes of a varying $M$ are less than that of a constant $M$. The Hubble constant tension is alleviated from larger than $5\sigma$ to be about $1$ to $2\sigma$ for a varying $M$, and the growth tension can be resolved after attributing the variation of $M$ to a modification of the effective Newton's constant.